1. Field of Invention
The present invention relates to an optical touch panel system and a positioning method thereof, in particular to such optical touch panel system and positioning method which utilize a light projection apparatus capable of selectively emitting light or reflecting external light to resolve the problem of blind zones.
2. Description of Related Art
Touch screen is an interactive apparatus for users to directly and intuitively operate application software on the screen. There are various types of touch screens, one of which is the optical touch panel.
FIG. 1 shows a prior art optical touch panel system 1, which is disclosed by U.S. Pat. No. 4,782,328. As shown in FIG. 1, the optical touch panel system 1 comprises two sensors 11 for capturing images of an object 13 on a touch control area 12. A processor 14 is coupled to the two sensors 11; it analyzes the images generated by the sensors 11 to determine the sensing paths 15 linking the object 13 to the two sensors 11. The processor 14 calculates the coordinate of the object 13 according to the sensing paths 15.
FIG. 2 shows another prior art optical touch panel system 2 which is disclosed by Taiwanese Patent Publication No. 201003477 (counterpart U.S. Pat. No. 7,689,381 B2). The optical touch panel system 2 comprises a mirror 21, two light sources 22, an image sensor 23 and a processor 24. The mirror 21 and the two light sources 22 are located at the periphery of a touch control area 28. The mirror 21 reflects the object 25 to generate a mirror image 26. The image sensor 23 captures the real image of the object 25 and the mirror image 26. The processor 24 analyzes the sensing paths 27 passing the real image of the object 25 and the mirror image 26, and calculates the coordinate of the object 25 according to the two sensing paths 27.
In the optical touch panel system 2, when the two sensing paths 27 are too close to each other, the real image of the object 25 and the mirror image 26 overlap with each other, and the position of the object 25 cannot be obtained. As shown in FIG. 2, when the object 25 is in the region of the touch control area 28 near the side where no light source is provided, the precise position of the object cannot be detected because the real image of the object and the mirror image will overlap. This region is called the blind zone.
Taiwanese Invention Patent Application No. 098131423(FIG. 10 of U.S. Patent Publication No. 2010/0309169 also discloses a similar apparatus) provides an optical touch control apparatus, as shown in FIG. 3. The optical touch control apparatus 100a comprises a lighting device 120, an image detection module 130, two light guide bars (112a, 112b), and two stripe-like mirrors (114a, 114b). The light guide bars (112a, 112b) are close to each other, and the stripe-like mirrors (114a, 114b) are close to each other. The light guide bars (112a, 112b) and the stripe-like mirrors (114a, 114b) are disposed around the four sides of a rectangle. The inside area of the rectangle is a sensing area 116. The light guide module 110a includes two stripe-like mirrors (114a, 114b), so each point being touched in the sensing area 116 generates three mirror images. The image detection module 130 captures the real image of the object B and the mirror images B1-B3, and calculates the position of the object B according to these images. The area of the blind zone 150a in the optical touch control apparatus 100a is reduced, but the problem of the blind zone still exists. That is, the dark images of B and B1 partially overlap with each other and the dark images of B2 and B3 partially overlap with each other. In addition, infinite reflection occurs in the neighborhood of the corner between the two stripe-like mirrors (114a, 114b). For this reason, U.S. Pat. No. 7,274,356 B2 disposes anon-reflective region at this corner to resolve the problem.